Neutrophils and monocytes migrate out of blood vessells in the course of inflammatory reactions, a process which is presumed to result from generation of extravascular chemotactic factors. The first step in such a reaction may be presumed to be adherence of the leukocyte to vascular endothelial cells. it is the mechanisms by which chemotactic factors induce a recognition of passing leukocytes by the endothelium, which is the focus of this proposal. Endothelial cells will be grown from rabbit, bovine (and human) pulmonary arteries by techniques which completely avoid the need for proteases. Justification for use of arterial endothelial cells comes from our demonstration that C5a des Arg applied to the adventitial surface of rabbit carotid arteries induces neutrophil attachment to and migration through the endothelium. This in vivo system for study of leukocyte endothelial interaction, as well as that of isolated perfused arteries will be included in the investigations. Chemotactic factors will include purified C5a, purified leukotriene B4, semisynthetic acetylglycerylether phosphorylcholine (AGEPC), and F-met-leu-phe (FMLP) for neutrophils as well as C5a des Arg, Asp-Arg-Val-Tyr (AAVT) and a neutrophil-derived factor for monocytes. Questions to be addressed include the following. Do chemotactic factors induce changes in endothelial cells which promote leukocyte binding? Are such stimulated endothelial cells able to 'recognize' different leukocytes? Do chemotactic factors also alter the leukocyte surface to cause them to adhere to the endothelium? Do either of the cells secrete proadhesive factors? Can we identify and characterize the adherence sites and components? This last question will be pursued in part by the use of monoclonal antibodies prepared against leukocyte and endothelial cell surfaces. In these studies we hope to characterize some of the mechanisms underlying the first stage of leukocyte emigration into inflammatory sites, namely adherence to the endothelium. Concomitant in vivo components in this proposal will provide validity to the observations. Finally, we should effectively set the stage for future examination of the transvascular migratory process.